In a typical automated high volume manufacturing facility for fabricating electronic products, such as computer visual displays or television receivers, the operation of each electronic circuit in the product is automatically tested by a functional tester. The functional tester typically comprises a test fixture for receiving a printed circuit board carrying components of the electronic circuit to be tested. Generally, a test fixture includes a base and a cover pivotably mounted on the base. The printed circuit board to be tested is placed on the base and the cover is then closed over the base for safety. An array of test pins is provided in the base. The pins are positioned to engage solder pads on the printed circuit board received in the fixture. Test instrumentation is connected to the pins to test the function, or at least to ensure continuity of connection of electronic components soldered to the pads. The instrumentation identifies a failure condition if, for example, the solder joint at the pad is defective, or if the component soldered to the pad has failed.
Some electrical components, such as connectors, have electrical contacts on both sides of the printed circuit board. To facilitate testing such components, it is usual to supply test pins on both the base and the cover of the fixture so that both sides of the component can be probed. The accuracy of insertion of such components into the circuit board is critical to the effectiveness of the test pins on the cover part of the fixture. This is especially true in the case of so-called "header" connectors, i.e., a male part of a multi-pin connector. Headers typically comprise an array of upstanding pins engaging a multiple contact socket. Ideally, the header is soldered to the circuit board, in a pin-in-hole arrangement (rather than, for instance, surface mount), keeping the pins perpendicular to the board. However, it is not unusual for the header to be soldered in place to the pins at a slight angle from the perpendicular direction. Although this does not affect the general function of the header, it does affect the functional testing, because the test pins positioned to probe the header pins from above miss their targets. The test instrumentation may thus erroneously indicate a failing condition. Furthermore, the test pins mounted in the cover of the fixture may be bent or otherwise damaged during use, leading to reduced reliability. The populated printed circuit board is placed on a "bed of nails" tester for functional testing. In the bed of nail tester, test pins are selectively brought up from the test bed to engage with pads on the printed circuit board.